1. Field of the Invention
This nonprovisional application claims priority under 35 U.S.C. xc2xa7119(a) on Patent Application No. 2001-396792 filed in JAPAN on Dec. 27, 2001, which is herein incorporated by reference.
The present invention relates to a distance measuring apparatus, and particularly to a distance measuring apparatus which carries out so called multi-point distance measurement with a plurality of distance measurement areas.
2. Description of the Related Art
In distance measuring apparatuses of cameras, for example, distance measurement apparatuses employing so called a multi-point distance measurement method in which a plurality of areas are set in a shooting range, distances of a distance measurement object are measured for respective distance measurement areas, and any one of the distances is employed as a measured distance have been known.
In multi-point distance measurement, the shortest distance of distances determined for a plurality of distance measurement areas is generally employed as a measured distance, but there are problems such that an undesired object located at a short distance may exist in the area around the shooting range, and in this case, the distance of the undesired object is employed as a measured distance. Thus, it is proposed in Japanese Patent No. 2620235 and Japanese Patent No. 2772028 that if an object located at a distance shorter than a predetermined distance is measured in a distance measurement area around the shooting range, the distance measured in the distance measurement area is not employed.
However, even if an object located at a distance shorter than a predetermined distance is detected in a distance measurement area around the shooting range, the object is not necessarily an undesired object for a photographer, and thus determining whether or not the distance is to be employed as a measured distance according only to whether it is shorter than a predetermined distance or not may result in erroneous distance measurement.
The present invention has been devised in view of the above situations, and the object thereof is to provide a distance measuring apparatus in which a suitable distance is employed as a measured distance from distances measured for a plurality of distance measurement areas, thereby preventing erroneous distance measurement.
In order to attain to the above-mentioned object, the present invention is directed to a distance measuring apparatus in which a plurality of distance measurement areas are set in an image formation range of a sensor on which an image of a distance measurement object is formed, distances of the distance measurement object are measured for respective distance measurement areas according to signals obtained from the sensor, and any one of the measured distances for respective distance measurement areas is employed as a measured distance, the distance measuring apparatus comprising: an employed distance selecting device in which the distance of the distance measurement object is three-way divided into a very short distance range, a short distance range and a moderate to long distance range, and a condition of whether a result of measuring distances of the distance measurement object is consistent with a case where only the distance measured in any one of distance measurement areas located at ends of the plurality of distance measurement areas belongs to the very short distance range and all the distances measured in other distance measurement areas belong to the moderate to long distance range is set up, wherein: if the condition is not satisfied, a closest distance of all distances measured for the plurality of distance measurement areas is employed as the measured distance, and if the condition is satisfied, a closest distance of the distances belonging to the moderate to long distance range of distances measured for the plurality of distance measurement areas is employed as the measured distance.
According to the present invention, even if the distance of an object located at the very short distance is measured in any one of the endmost distance measurement areas of a plurality of distance measurement areas, it is not determined according only to the above fact that the distance belonging to the very short distance range is not employed as a measured distance, but instead it is determined that the distance belonging to the very short distance range is not employed as a measured distance only when all the distances measured in other distance measurement areas belong to the moderate to long distance range, and then the shortest distance of distances belonging to the moderate to long distance range is employed as a measured distance. On the other hand, if any of the distances measured in other distance measurement areas belongs to the short distance range which is closer than the moderate to long distance range, the object located at the very short distance is likely one of the desired objects for shooting, and therefore the distance belonging to the very short distance range is employed. In this way, a suitable distance can be employed as a measured distance from distances of the distance measurement object measured in a plurality of distance measurement areas, thus making it possible to reduce the frequency of erroneous distance measurement. Furthermore, the plurality of distance measurement areas are not necessarily arranged in the horizontal direction, but may be arranged in the vertical direction or in the horizontal and vertical directions, and the above described endmost distance measurement areas refer to distance measurement areas located at the left and right ends for the horizontal direction, and refer to distance measurement areas located at the upper and lower ends for the vertical direction.
Preferably, the very short distance range is a range in which a short distance warning is given.
Preferably, the plurality of distance measurement areas set in the image formation range of the sensor are changed depending on an angle of view. For example, five distance measurement areas are set in the left-to-right direction for the wide angle of view, and three distance measurement areas are set in the left-to-right direction for the tele angle of view.